EXPEEIMEXTS ON VEGETATION IX SOLUTIONS. 381 



not be said to live.* In the experiments made without soda, it 

 was found that the plant could dispense with this substance at 

 first, but its progress was soon arrested if the soda was com- 

 pletely withdrawn. The nitrate of lime of the normal solution 

 was in another experiment replaced by a corresponding quan- 

 tity of nitrate of magnesia. The growth of the maize plant 

 was after a short time much retarded, only a few small, thin 

 leaves being developed. By the addition of a little nitrate of 

 lime to the growing plant, the most remarkable change was, 

 however, produced. Scarcely five hours elapsed before the 

 growth of the plant, which had been stationary for four weeks, 

 awakened to a new life, and proceeded from this time forth in 

 the best manner possible. A plant without the after addition 

 of nitrate of lime remained stationary, making no progress 

 whatever : the maize plant, therefore, requires lime immediately 

 after the commencement of its growth. 



In an experiment in which the magnesia was replaced by 

 nitrate of lime, the same result was obtained as when lime was 

 wanting. In this case, also, the vegetation was very poor. A 

 supply of magnesia, in the form of nitrate, exerted here also 

 the most favourable action, only the effect was not so quickly 

 produced as in the case of lime. 



Even by the complete withdrawal of nitric acid the maize- 

 plant did not grow. In these experiments it is true the alkalies, 

 as well as the alkaline earths, were in part supplied in the form 

 of sulphates and chlorides. Chlorine and sulphuric acid, how- 

 ever, are required only to a limited extent in the vegetable 

 organism. The same holds good in the experiment without 

 nitrogen. According to these experiments, therefore, a plant 

 is not developed if one of its elements of food is wanting, and 

 the complete replacement of one element of food by another 

 one similar to it, is hence completely out of the question. The 

 result may, however, be different with the reciprocal partial 

 replacement of similar elements of food ; and Stohmann is about 

 to take up this question. 



The form in which the food was supplied was the following. f 



* Compare Knop, 'Chem. Central Bl. 1862,' s. 257. 



t To form a complete solution of all matters, and to remove the alkaline re- 

 action, the fluid was first properly diluted with water and so much weak hydro- 

 chloric and later phosphoric acid was added as to make the reaction distinctly 

 feebly acid. 



